rd2002

i think jwxie518 means you need to use the same model rams of the same brand because the specification might be different among ram manufacturers.
also, to begin with, you need to check how many gb of ram your laptop supports, as well as the ram model. secondly, you might want to make sure your laptop is running a 64-bit system if you want to utilize all 4gb of ram; otherwise, it is very likely that your system can only recognize around 3gb ram even if you have 4gb installed.